Try and calm the child and say that you won't sit on Erin. If you tell the young girl that Erin isn't real at that age, they may have social issues later.
Answer:
62.5 %
Explanation:
Let the initial intensity of unpolarized light is Io.
After first polariser the intensity of light becomes I'.
So, 
Now it passes through another polariser. The angle between the first polariser and the second polariser is given by Ф. The intensity is I''.
According to the law of Malus

Here, Ф = 30 degree

The percentage change in the intensity is given by

= 62.5 %
Answer:
v = 0.99 c = 2.99 x 10⁸ m/s
Explanation:
From the special theory of relativity:

where,
v = speed of travel = ?
c = speed of light = 3 x 10⁸ m/s
t = time measured on earth = 90 years
t₀ = time measured in moving frame = 6 months = 0.5 year
Therefore,

<u>v = 0.99 c = 2.99 x 10⁸ m/s</u>
Answer: 430 nm
Explanation:
For 257 kJ to dislodge one mole of electrons we need,
275 x 10^3 / 6 x 10^23 = 4.6 x 10^-19
Using Einstein’s relationship between energy, frequency and wavelength
E = hf = h x (c/landa)
Therefore
Landa = h x (c/E) = 6.6 x 10^-34 x (3 x 10^8 / 4.6 x 10^-19 = 4.3 x 10-7 m.
In nm, landa = 430 nm